Electrical pulse generating system



June 17, 1969 L. H. SEGALL ETAL 3,450,942

I ELECTRICAL PULSE GENERATING SYSTEM Filed April 10. 1967 INVENTORS LOUIS H. SEGALL IRVING E. LINKROUM ATTO NEYS United States Patent 3,450,942 ELECTRICAL PULSE GENERATING SYSTEM Louis H. Segall, Sidney, and Irving E. Linkroum, Hancock, N.Y., assignors to The Bendix Corporation, a corporation of Delaware Filed Apr. 10, 1967, Ser. No. 629,674

Int. Cl. H05b 37/02 US Cl. 315209 22 Claims ABSTRACT OF THE DISCLOSURE An electrical pulse generating system wherein two levels of energy are selectively supplied to a single load output from a common source. The source is selectively connectible to different points of two linked condenser discharge circuits to vary the division of input energy to simultaneously charge the storage condensers in said circuits. One said circuit is a power circuit for supplying energy to the output through a normally nonconductive control gap and the other is a trigger circuit for ionizing and rendering said gap conductive in response to the combined voltages on the storage condensers of both circuits when the sum of said voltages attains the breakdown value of a second control gap in the trigger circuit.

This invention relates to electrical apparatus and in particular to a spark generating system for providing a succession of spark gap discharge voltages at different selected energy levels from a single energy supply source.

A principal object of the invention is to provide an ignition system capable of selectively providing dual energy levels to a spark-gap discharge device for start and continuous operation of a combustion engine.

Another object of the invention is to provide an ignition system capable of selectively delivering two levels of energy to a storage device for discharge through a spark-gap discharge device.

Another object of the invention is to provide an ignition system having a spark-gap discharge device, including electrode means external thereto for receiving high energy impulses at both high and low energy inputs to said device for ionizing the same.

Another object of the invention is to provide an igni tion system for start and continuous operation of a combustion engine at two energy levels, the components of said system, although being rated for the higher energy level, are operated at low energy levels over considerable time intervals thereby subjecting the components to less stress and strain thereby assuring longer life of all com ponents including the gap electrodes and thus creating greater operating efiiciency of the overall system with resulting fewer breakdowns, reduced maintenance costs and greater reliability over the extended time period.

The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be understood, however, that the drawing is for the purpose of illustration only and is not intended as a definition of the limits of the invention.

The single figure of the drawing is a diagram illustrating one form of electrical circuit embodying the invention.

The embodiment of the invention illustrated in the accompanying drawing is, by way of example, shown in the form of a circuit for apparatus adapted for use as an ignition system in combustion engines and so-called jet and gas turbine engines.

As shown in the drawing, one suitable embodiment of the invention comprises, as a source of electrical energy,

an alternating current generator 10 which may be connected to the remainder of the circuit by means of a single-pole, double-throw switch 11, interposed in the supply leads 12 and 13, the input to the circuit under consideration. Each input lead has connected thereto suitable encased low pass filter means 15, 16 for filtering out unwanted radio frequencies, noise frequencies and the like thereby preventing said extraneous frequencies from feeding back to the generator source and to other apparatus supplied thereby. In the particular embodiment shown, the filter means comprises by-pass condensers connected beween ground (which may be the shielded case 17) and each power supply line, there being an inductance or choke coil interposed in each power supply line between the by-pass condensers and the power source. The filters are conveniently contained in housing 17, and form no part of the present invention. The power supply lines beyond filters 15, 16 are designated 18 and 19.

The lines 18 and 19 are connected to the opposite ends 20 and 21 respectively of an inductance coil 22. A voltage divider network 23 is connected between terminal 20 and ground, and consists of a pair of variable resistors 24 and 25, series connected, with their common terminal 26 connected to one end 27 of a primary coil 28 of a stepup type transformer 29, the opposite end 30 of the said primary coil being connected to terminal 21 of the inductance coil 22.

The secondary coil 30 of transformer 29 drives a relatively low voltage rectifier circuit 31. The rectifier circuit consists of a series connected rectifier 32 at one extremity of the coil 30 and a pair of capacitors 33 and 34, each capacitor having one terminal thereof connected to one electrode of the rectifier and the other terminal connected together to form a single connection 3411 at the other extremity of transformer coil 30. A spark gap 35 has one terminal or electrode 36 thereof connected to the high side of capacitor 34 and the other terminal 37 connected to the primary side 38 of a pulse-transformer 39. The pulse transformer 39 is designed to provide a high degree of voltage amplification in the form of an output pulse across its secondary coil 40. One extremity of the coil 40 is connected to an external electrode 41 suitably attached to the external surface of another spark-gap device 42. The other extremity of the coil 40 is connected to an electrode 43 of the said spark-gap device 42.

The spark gap 42, in the illustrated embodiment of the invention comprises a glass enclosure having suitably mounted and supported therein the spark-gap internal electrodes 43 and 44 appropriately separated, the glass enclosure having externally attached thereto to a surrounding metal foil which represents the third electrode 41, and is connected to the pulse transformer secondary 40 as previously stated.

A relatively high voltage rectifier circuit connected to the same supply source is also provided and comprises a transformer having one end of its primary winding 51 connected to terminal 21 of inductance coil 22 and the other end grounded. The secondary winding 52 of transformer 50 drives a voltage doubling circuit 53 consisting of a diode 54 having one terminal thereof connected to the high side 55 of coil winding 52 and polarized in one direction, and another diode 56 having also one terminal thereof connected to the same coil winding terminal 55, but polarized oppositely to diode 54. A resistor 57 is connected to the other terminal of diode 54 and grounded. A pair of capacitors 59 and 60 are series connected between the other terminal 61 of diode 56 and ground, and the mid-point 62 of the series connected capacitors is connected to the low side 58 of secondary coil 52 of transformer 50. The voltage doubling circuit operates in the usual manner in that when the voltage supply is in one phase, only diode 56 conducts and it will conduct in one direction only and thereby cause capacitor 59 to charge in one direction. Upon phase reversal of the supply voltage, diode 54 alone conducts causing capacitor 60 to charge, the charge being in the same direction as that applied to capacitor 59. Since both capacitors are in series their voltages will add thus doubling the source voltage.

The capacitor terminal 61 has connected thereto a resistor 63, the opposite end of the resistor being connected to a terminal 65 of storage capacitor 64, the other terminal of the capacitor 64 being grounded. The ungrounded terminal 65 of capacitor 64 is connected to the low side of capacitor 34 or to terminal 34a, the storage capacitors 34 and 64 being in series for discharge across gap 35 regardless of the positioning of source potential switch 11. A high ohmic value resistive element 66 is connected across and in parallel with capacitor 64 to allow residual leakage therefrom after the cyclical discharge of the said capacitor.

The high side terminal 65 of the capacitor 64 is connected to electrode 44 of spark gap 42 and has also connected thereto one terminal 70 of a capacitor 71, the other terminal thereof terminating in one of the extremities 72 of a primary winding 73 forming part of a pulse transformer 74. The other end 75 of primary winding 73 is connected to the other electrode 43 of the spark-gap device 42. The secondary winding 76 of transformer 74 has one extremity thereof also connected to spark gap terminal 43, the other extremity 77 of the winding being connected to discharge gap device 80 which contains the usual spark gap 81 shunted by a resistance 82 which may be in the form of a semi-conductive surface across the spark gap. The other side of the discharge gap device 80 is connected to ground. A low ohmic valued resistance element 83 has one terminal thereof connected to gap electrode 43 and the other extremity grounded. In the particular embodiment described, pulse transformers 39 and 74 are shown as high ratio step-up auto-transformers, but other types of pulse transformers may be used to carry out the invention shown herein.

For high level energy excitation the source voltage is switched by switch 11 to the input lead side 12 so as to place full line voltage which may be in the order of 100 to 120 volts at 400 cycles across the transformer primary 51 of transformer 50. The voltage appearing across transformer 29 is considerably reduced because of the voltage divider network consisting of the resistors 24 and 25. Because of the substantially reduced voltage across transformer 29, the discharge capacitor 34 will correspondingly have a reduced voltage thereacross. On the other hand, because of the full excitation applied to transformer 50, the voltage appearing across discharge capacitor 64 will be relatively high. The discharge capacitors 34 and 64 in the embodiment shown are series additive and the full additive voltage across both appears across the spark gap 35. As a result of this high voltage, spark gap 35 ionizes and breaks down or conducts and permits only capacitor 34 to discharge therethrough and through the primary 38 of transformer 39 thereby exciting the said transformer. The discharge current also proceeds through the primary 73 of the high frequency transformer 74, through the high frequency capacitor 71 and finally completing the circuit back to the low side of capacitor 34. As a result of the discharge of capacitor 34, a high voltage pulse is produced in the secondary winding 40 of pulse transformer 39. This high voltage pulse is applied across the output electrode 43 or spark gap 42, and the external foil electrode 41 thereof. The high voltage appearing across electrodes 41 and 43 of spark gap 42 causes ionization of the gases therein. The condenser 71, which is chargeable in incremental steps to the same voltage as that appearing across storage condenser 64, is connected across the spark gap 42, and the voltage thereon likewise appears across the same gap and causes the gap to trigger or conduct. The condenser 71 will now discharge through the conductive spark gap 42 and the resulting current flow will excite the primary coil 73 of transformer 74. The secondary coil 76 of transformer 74 will accordingly have induced therein a high voltage which will be impressed across the discharge gap 80 causing it to conduct. Upon conduction, the storage capacitor 64 will discharge therethrough to cause the spark necessary to create ignition.

The above represents operation of the system for supplying high level energy, as for example when starting a combustion engine. For continuous operations as in the low level energy mode, the power source 10 is switched over, by switch 11 to input lead 13. The full line power voltage now appears partly across inductor 22 and the primary winding 51 of transformer 50 which is in series therewith. The voltage across coil 22 appears substantially across the primary coil 28 of transformer 29, so that the said transformer will be more heavily energized than in the previously described high level energy case. Also since transformer 50 has less voltage applied thereto across its primary, it will be less heavily energized than in the previous high level energy mode. This results in storage capacitor 34 being charged to a higher voltage level and discharge capacitor 64 being charged to a lower voltage level. However, since both capacitors 34 and 64 are series additive, this voltage summation will still be sufficient to cause ionization and conduction of spark gap 35. Upon conduction of the spark gap 35, the operation previously explained repeats itself in that the spark gap 42 will again be ionized because of the peak voltages appearing across the electrodes 41 and 43 thereof, and will accordingly breakdown and conduct. Hence, discharge capacitor 64, having a reduced voltage because of the lower voltage appearing across transformer 50, will nevertheless discharge through the spark gap 42 after its breakdown. It can be appreciated here that because the voltage appearing across the discharge capacitor 64 is reduced over extended periods of time, i.e. during continuous low level mode operation of the combustion engine, the life of the said capacitor will be considerably extended and the probability of its failure in operation considerably reduced. Hence, reliability and cost considerations are considerably enhanced.

The circuit as shown in FIGURE 1 representing a particular embodiment of the invention may have the particular component parts thereof rated in the following manner depending upon whether the circuit is operating at the low or high energy levels:

(1) High level operation, capacitor 34, typically rate at .01 micro-farad and 1.5 kv., will be charged to 0.5 kv. and capacitor 64, typically rated at 5.5 micro-farad and 2.5 kv., will be charged to 2.0 kv., the combined voltages, 2.5 kv. being sufficient to cause conduction of spark gap 35, which is rated for breakdown purposes at 2.5 kv. Pulse transformer 39, will develop a voltage across its secondary 40, when capacitor 34 discharges, that is approximately 8.0 kv., enough to cause ionization and conduction of spark gap 42. The gap 42 is rated at 2.5 kv., but because of ionization it will break down at a reduced voltage, or 2 kv.; this latter voltage appearing on capacitor 71 which is rated at 0.25 micro-farads and 2.5 kv.

(2) Low level operation, capacitor 34 is charged to 1.5 kv. and capacitor 64 is charged to 1.0 kv. and their combined voltages is equal to the 2.5 kv., of the previous example, or high level operation and the operative sequence is repeated.

Thus it is seen that the ignition circuit provides two levels of energy output, one at 2 kv. and one at 1.0 kv., and that the output energy level can be selected by switching the power input selector switch.

Although only one embodiment of the invention has been illustrated in the accompanying drawing and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto but that it may be embodied in other specifically defined circuits. For example, other well-known sources of pulsating or alternating current sources may be provided in lieu of the generator-transformer combination illustrated. Additionally, the various parts of the circuit may be rearranged with respect to each other without appreciably affecting the operation of the circuit.

What is claimed is:

1. Electrical apparatus for generating electrical pulses comprising a first spark-gap device, a second spark-gap device, first capacitor means connected to said first sparkgap device, second capacitor means connected to said second spark-gap device and including a capacitor connected in series with said first capacitor means across said first spark-gap device, energy means for charging said first and second capacitor means to pre-select voltage levels, and transformer means interposed between said first and second spark-gap devices for receiving discharge currents from said series connected capacitor and first capaitor means upon conduction of the first spark-gap device at the said pre-selected voltage levels and impressing high voltages at the second spark-gap device to cause the conduction thereof, thereby allowing the second capacitor means to discharge therethrough to a load circuit.

2. An ignition system for delivering energy pulses to a combustion engine from a single power source comprising a first spark-gap discharge device, a second spark-gap discharge device, first storage means connected to said first device, second storage means connected to said second device and including a capacitor connected in series with said first storage means across said first spark-gap discharge device, voltage charging means selectively connected to said power source and storage means for selectively charging said first and second storage means to pre-selected energy levels, high voltage means interposed between said first and second gap discharge devices for receiving the discharge currents from said series connected capacitor and first storage means upon breakdown of the first spark-gap discharge device and impressing high voltages at the second discharge device to cause the ionization thereof, thereby causing the second spark-gap discharge device to break down and cause the second storage means to discharge its stored energy therethrough, and means including an ignition discharge device for receiving said energy at the preselected levels for producing an ignition spark at the said combustion engine.

3. Electrical apparatus according to claim 2 wherein said voltage charging means further comprises voltage multiplication circuits including electron discharge rectifier devices and protective means therefor.

4. Electrical apparatus according to claim 3 wherein said protective means includes resistive elements in circuit with the electron discharge rectifier devices to limit the fiow of currents upon the discharge of the said second storage means.

5. Electrical apparatus according to claim 2 wherein said energy receiving means includes a high ratio step-up transformer for producing high voltages across the ignition discharge device.

6. Electrical apparatus according to claim 2 wherein said ignition discharge device is a shunted discharge gap disposed to conduct and effect ignition.

7. In electrical pulse generating apparatus a first condenser, a second condenser, means for simultaneously charging said condensers, means connecting said condensers in series in a discharge circuit therefor comprising a normally non-conductive control gap and the primary winding of a transformer, a normally non-conductive control gap device having two main electrodes and a triggering electrode, said transformer having a secondary winding connected across said triggering electrode and a said main electrode, and said second condenser being connected in a discharge circuit therefor across said main electrodes, whereby when the control gap is rendered conductive by the sum of the charges on said condensers, the gap between said main electrodes is ionized by the voltage across said secondary winding and thereby rendered conductive to the discharge of said second condenser.

8. Electrical apparatus as defined in claim 7 wherein the spark-over voltage of said control gap device exceeds the maximum charge attained by said second condenser.

9. Electrical apparatus as defined in claim 7 wherein the first condenser is charged by said charging means more rapidly than said second condenser.

10. Electrical apparatus as defined in claim 7 wherein the second condenser is charged by said charging means more rapidly than said first condenser.

11. Electrical apparatus as defined in claim 7 wherein said charging means comprises a first power transformer having a primary winding and a secondry winding connected to charge said second condenser, an inductance connected in series with said primary winding across an alternating current power supply and a second power transformer having a primary winding connected across said inductance and a secondary winding connected across said first condenser.

12. Electrical apparatus as defined in claim 7 wherein said main electrodes are in a sealed capsule and said triggering electrode is external of the capsule.

13. Electrical apparatus as defined in claim 12 wherein said triggering electrode comprises a foil ribbon surrounding said capsule.

14. In electrical pulse generating apparatus a first power transformer, a second power transformer, a source of electrical energy, means for connecting said source to the primary windings of said transformers to divide the energy of the source between said transformers in selected ratios, a first condenser and a second condenser connected to be simultaneously charged by said first and second transformers, respectively, a normally non-conductive control gap, said condensers being connected in series in a discharge circuit therefor across said gap, a triggering transformer having its primary winding in said discharge circuit, a second normally non-conductive control gap having input, output and triggering electrodes, said second condenser being connected across said input and output electrodes and the secondary winding of the triggering transformer being connected across said triggering and output electrodes, whereby when said first-named control gap is rendered conductive by the sum of the charges on said condensers, the second control gap is ionized and thereby rendered conductive to the charge on the second condenser.

15. In electrical pulse generating apparatus, first energy storage means including a first capacitor, second energy storage means including a second capacitor, means for charging said first and second energy storage means, a first normall non-conductive control gap device having a predetermined spark-over voltage, means connecting said capacitors and said gap device in series in a discharge circuit whereby said gap device is rendered conductive when the sum of the charges on said capacitors attains said spark-over voltage, a second normally nonconductive control gap device, means connecting the latter across said second capacitor and across the remainder of said second energy storage means, and means for applying the discharge of said capacitors through said first control gap device to said second control gap device to render the latter conductive to the charge on said second energy storage means.

16. Electrical pulse generating apparatus as defined in claim 15 wherein said remainder of the second energy storage means comprises a third caapcitor having a capacity substantially greater than the capacity of either of said first and second capacitors.

17. Electrical pulse generating apparatus as defined in claim 15 comprising an igniter gap connected in series with said second control gap device across said remainder of said second energy storage means.

18. Electrical pulse generating apparatus as defined in claim 17 comprising a transformer having a primary winding connected in series with said second capacitor across said second control gap device and a secondary winding connected in series with said igniter gap and second control gap device.

19. In electrical pulse generating apparatus, a first spark-gap device, a second spark-gap device, a first capacitor, a second capacitor, means for charging each of said capacitors, means connecting said capacitors and said first spark-gap device in series in a first discharge circuit, means connecting said second capacitor and said second spark-gap device in series in a second discharge circuit, and means responsive to the discharge of said first and second capacitors through said first discharge circuit when the sum of the charges on said capacitors attains the spark-over voltage of said first spark-gap device to render said second spark-gap device conductive to the charge on said second capacitor.

20. Electrical pulse generating apparatus as defined in claim 19 wherein said means for charging said capacitors comprises a source of electrical energy, a first transformer connected to charge said first capacitor, a second transformer connected to charge said second capacitor, and means for selectively connecting the primary windings of said transformers in seriees or in parallel across said source.

21. Electrical pulse generating apparatus as defined in claim 20 comprising a voltage divider for controlling the voltage impressed across the primary winding of said first transformer.

22. Electrical pulse generating apparatus as defined in claim 19 wherein the spark-over voltage of said second spark-gap device exceeds the voltage attained by the charge applied to said second capacitor.

References Cited UNITED STATES PATENTS 2,978,611 4/1961 Segall 315-180 3,127,540 3/1964 Collins 315-180 3,146,376 8/1964 Segall et al. 3l5--161 LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 

